1. Field of the Invention
This invention relates to a control information transmitting method, a transmitter, and a transmitting and receiving apparatus, and more particularly, is applicable to a cellular wireless communication system.
2. Description of the Related Art
In the cellular wireless communication systems, areas for providing communication service are segmented into cells having a desired size to set a base station as a fixed station in the cell. A communication terminal device provided as a mobile station wirelessly communicates with the base station which is in the most preferable state for communication.
In this type of cellular wireless communication system, there is a case where high transmission power is needed to communicate or there is a case where low transmission power can communicate sufficiently, depending on the location of the mobile station. In the cellular wireless communication system, the base station and the communication terminal device check the reception power (or the quality of reception signal) between each other and inform each other of the checked result to form a feedback loop, so that communication under minimum transmission power, so-called transmission power control, is performed. Thereby, the cellular wireless communication system can efficiently communicate under minimum transmission power and reduce power consumption comparing to the case of communicating under constant power, so that the communication terminal device obtains the especial effect that battery life can be extended.
In the conventional cellular wireless communication system, control information for power control is transmitted to a communication partner to control the transmission power. However, no measures have been taken to transmit the control information exactly, and it is necessary to be improved.
In view of the foregoing, an object of this invention is to provide a control information transmitting method which can transmit the control information for controlling transmission power exactly and a transmitter and a transmitting and receiving apparatus which use the method.
The foregoing object and other objects of the invention have been achieved by the provision of a control information transmitting method and a transmitter and a transmitting and receiving apparatus.
In a control information transmitting method of transmitting, to a communication partner, control symbols obtained by assigning control information for controlling transmission power to symbols of phase modulation, so as to control the transmission power of the communication partner, the control information which indicates raising the transmission power of the communication partner and the control information which indicates lowering the transmission power of the communication partner are assigned to a pair of symbols having the longest Euclidian distance between the symbols from among the symbols of phase modulation.
Further, the control information transmitting method uses control information which indicates raising the transmission power of the communication partner, control information which indicates lowering the transmission power of the communication partner, and control information which includes the contents of the control information previously sent to the communication partner and which indicates holding the transmission power of the communication partner, as the control information, so as to transmit to the communication partner the control symbols to which one of the control information is assigned.
Further, the control information transmitting method uses a plurality of rectangular subcarriers to communicate with the communication partner, and assigns the control symbols to the subcarriers, excluding the vicinity of both ends and center of the band, from among plurality of the subcarriers and then transmits them.
Further, in the control information transmitting method, using xe2x80x9cnxe2x80x9d band slots comprising a plurality of rectangular subcarriers for communication with the communication partner, xe2x80x9ckxe2x80x9d subcarriers for transmitting control symbols are respectively provided in the band slots (where, nxe2x89xa7k) from among the xe2x80x9cnxe2x80x9d band slots and then the control symbols are assigned one by one to the subcarriers for transmitting the control symbols to be transmitted.
Furthermore, a transmitter for transmitting to a communication partner control symbols obtained by assigning control information for controlling transmission power to symbols of phase modulation, so as to control the transmission power of the communication partner, comprises a symbol producing means for producing the control symbols by assigning the control information which indicates raising the transmission power of the communication partner and the control information which indicates lowering the transmission power of the communication partner to a pair of symbols having the longest Euclidian distance between the symbols from among the symbols of phase modulation, and a transmitting means for transmitting the control symbols to the communication partner.
Further, the transmitter comprises a symbol producing means for producing the control symbols by using, as the control information, control information which indicates raising the transmission power of the communication partner, control information which indicates lowering the transmission power of the communication partner, and control information which includes the contents of the control information previously sent to the communication partner and which indicates holding the transmission power of the communication partner, to assign one of the control information to the symbols, and a transmitting means for transmitting the control symbols to the communication partner.
Furthermore, a transmitting and receiving apparatus for receiving, from a communication partner, control symbols obtained by assigning control information for controlling transmission power to symbols of phase modulation, so as to control its own transmission power based on the control symbols, comprises a transmitting means for transmitting a predetermined signal to the communication partner, a receiving means for using, as the control information, control information which indicates raising transmission power, control information which indicates lowering transmission power, and control information which includes the contents of the control information previously sent and which indicates holding transmission power, and for receiving the symbols to which one of the control information is assigned, and a control means for performing error correction on the received control information based on the carrier to interference power ratio at the time when the control information is received, if the control information previously received is inconsistent with the control information received this time.
Further, in the transmitter for transmitting, a plurality of rectangular subcarriers are used to communicate with the communication partner, and the control symbols are assigned to the subcarriers, excluding the vicinity of both ends and center of the band, from among plurality of the subcarriers, and then are transmitted.
Further, in the transmitter for transmitting, using xe2x80x9cnxe2x80x9d band slots comprising a plurality of rectangular subcarriers for communication with the communication partner xe2x80x9ckxe2x80x9d subcarriers for transmitting control symbols are respectively provided in the band slots (where, nxe2x89xa7k) from among the xe2x80x9cnxe2x80x9d band slots having the number of xe2x80x9cnxe2x80x9d, and then the control symbols are assigned one by one to the subcarriers for transmitting the control symbols to be transmitted.
Furthermore, in the transmitting and receiving apparatus, using xe2x80x9cnxe2x80x9d band slots comprising a plurality of rectangular subcarriers for communication, when xe2x80x9ckxe2x80x9d subcarriers for transmitting control symbols are respectively provided in the band slots (where, nxe2x89xa7k) among from the band slots, and then the same control symbols are assigned one by one to the subcarriers for transmitting the control symbols to be transmitted, the control symbols are composed in accordance with the carrier to interference power ratio of each band slot to decode the control information from the composed control symbols, and then its own transmission power is controlled based on the decoded control information.
Further, in the transmitting and receiving apparatus, using xe2x80x9cnxe2x80x9d band slots comprising a plurality of rectangular subcarriers for communication, when xe2x80x9ckxe2x80x9d subcarriers for transmitting control symbols are respectively provided in the band slots (where, nxe2x89xa7k) from among the xe2x80x9cnxe2x80x9d band slots, and then the same control symbols are assigned one by one to the subcarriers for transmitting the control symbols to be transmitted, the control symbols are picked up from the band slot having the most preferable carrier to interference power ratio to decode the control information, and then its own transmission power is controlled based on the decoded control information.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.